Hi WSNHosting,
FIRST, pls. CHECK, that your configuration files includes the protection ( pls. check it for apache AND nginx configuration files! ).
If it does and you still don't have the "htaccess" - equivalent, which Plesk uses to secure statistics, pls. consider to head over to:
=> HOME > Domains > YOUR-DOMAIN.COM > Password-Protected Directories
... and check if the setting for "
/plesk-stat" is available.
It it doesn't exist, pls. consider to add the desired folder to protect it as setup within standard creations over the Plesk Control Panel.